Methods and systems of adaptive antenna pointing for mitigating interference with a nearby satellite

ABSTRACT

Systems and methods are described herein for adaptive pointing operations of a mobile antenna system that can be used to provide communication with a target satellite over a large geographical area, while also satisfying interference requirements with one or more other satellites. In particular, the adaptive pointing operations described herein control pointing of a beam of the antenna system towards the target satellite in a manner that takes into consideration the interference requirements of the other satellites. In some embodiments, the mobile antenna system can provide non-interfering communication with the target satellite, over the entire or substantially the entire coverage area (or footprint) of the target satellite. In doing so, services such as Internet, telephone and/or television services provided by the target satellite can be delivered to users throughout most or all of the satellite&#39;s coverage area, while also satisfying interference requirements with other satellites.

CROSS-REFERENCE TO RELATED APPLICATIONS

This present Application for Patent is a Continuation of U.S. patentapplication Ser. No. 16/362,377 by Cross, et al, entitled “Methods andSystems of Adaptive Antenna Pointing For Mitigating Interference With aNearby Satellite” filed Mar. 22, 2019, which is a continuation of U.S.patent application Ser. No. 15/687,063 by Cross, et al., entitled“Methods and Systems of Adaptive Antenna Pointing for MitigatingInterference with a Nearby Satellite,” filed Aug. 25, 2017, which claimspriority to U.S. Provisional Application No. 62/398,031, entitled“Methods and Systems of Adaptive Antenna Pointing for MitigatingInterference with a Nearby Satellite,” filed Sep. 22, 2016, each ofwhich is assigned to the assignee hereof and expressly incorporated byreference herein for any and all purposes.

BACKGROUND

The present disclosure relates generally to satellite communications,and more specifically to systems and methods for using such systems toavoid excessive interference with one or more non-target satellitesduring communication with a target satellite.

An Earth-based antenna terminal for communication with a targetsatellite typically has high antenna gain and a narrow beam pointed atthe satellite, because of the large distance to the satellite and toavoid interference with other (non-target) satellites.

In order to satisfy interference requirements with other satellites, amobile antenna terminal may only be permitted to communicate with thetarget satellite while at certain geographic locations. In such a case,services provided by the target satellite are unavailable to users ofthe mobile antenna terminal while at these locations, even though theyare within the coverage area of the target satellite.

SUMMARY

In one embodiment, a method is described that includes pointing a beamof an antenna on a mobile vehicle in a target direction at a targetsatellite and communicating a signal with the target satellite via theantenna. The beam has an asymmetric beam pattern with a wide beamwidthaxis and a narrow beamwidth axis in the target direction. The methodfurther includes determining that an amount of interference in anon-target direction reaches a threshold due to the wide beamwidth axisof the asymmetric beam pattern. The method further includes, in responseto the determination, adjusting pointing of the beam to an offsetdirection away from the non-target direction and further communicatingthe signal with the target satellite via the antenna.

In another embodiment, an antenna system for mounting on a mobilevehicle is described. The antenna system includes an antenna having abeam for communicating a signal with a target satellite. The beam has anasymmetric beam pattern with a wide beamwidth axis and a narrowbeamwidth axis. The antenna system further includes a pointingadjustment mechanism to adjust pointing of the beam of the antenna. Theantenna system further includes an adaptive pointing system to controltransition of the pointing adjustment mechanism from a first operationalmode to a second operational mode in response an amount of interferencein a non-target direction reaching a threshold due to the wide beamwidthaxis of the asymmetric beam pattern. In the first operational mode, thepointing adjustment mechanism points the beam of the antenna in a targetdirection at the target satellite. In the second operational mode, thepointing adjustment mechanism adjusts pointing of the beam to an offsetdirection away from the non-target direction.

Other aspects and advantages of the present disclosure can be seen onreview of the drawings, the detailed description, and the claims whichfollow.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an example satellite communications system in whichan antenna system as described herein can be used to point towards atarget satellite, while also avoiding excessive interference with one ormore other satellites.

FIG. 2 is a block diagram illustrating an example antenna system on theaircraft of FIG. 1.

FIG. 3 illustrates a perspective view of an example of an antenna andpositioner of an example antenna system described herein.

FIG. 4A illustrates a perspective view of the beam of an exampleasymmetric beam pattern of an example antenna.

FIG. 4B illustrates an example half-power contour of the asymmetric beampattern of beam of FIG. 4A.

FIG. 5A illustrates an example acceptable geographic areas using thefirst and second operational modes for pointing the beam at the targetsatellite.

FIG. 5B illustrates pointing of the beam of the antenna for an examplegeographic location within the acceptable geographic area for using thefirst operational mode.

FIG. 5C illustrates pointing of the beam of the antenna for an examplegeographic location outside the acceptable geographic area for using thefirst operational mode.

FIG. 5D illustrates a cross-sectional view of the beam pattern of thebeam versus angle along the geo arc for the pointing example of FIG. 5C.

FIG. 5E illustrates a line representing an example flight path for theaircraft on the illustration of FIG. 5A.

FIG. 6 illustrates an example adaptive pointing operation for pointingthe beam of antenna at the target satellite.

DETAILED DESCRIPTION

Systems and methods are described herein for adaptive pointingoperations of a mobile antenna system that can be used to providecommunication with a target satellite over a large geographical area,while also satisfying interference requirements with one or more othersatellites. In particular, the adaptive pointing operations describedherein control pointing of a beam of the antenna system towards thetarget satellite in a manner that takes into consideration theinterference requirements of the other satellites. In some embodiments,the mobile antenna system can provide non-interfering communication withthe target satellite, over the entire or substantially the entirecoverage area (or footprint) of the target satellite. In doing so,services such as Internet, telephone and/or television services providedby the target satellite can be delivered to users throughout most or allof the satellite's coverage area, while also satisfying interferencerequirements with other satellites.

The antenna system includes an antenna with a beam having an asymmetricbeam pattern at some or all of the pointing directions towards thetarget satellite. The asymmetric beam pattern of the beam of the antennahas a narrow beamwidth axis and a wide beamwidth axis. As described inmore detail below, when the antenna system is at certain geographiclocations, the wide beamwidth axis of the beam can give rise toexcessive interference with one or more other (non-target satellites),if the beam were pointed directly at the target satellite.

The antenna system described herein can avoid the excessive interferencethat could result due to the wide beamwidth axis of the beam, therebyallowing non-interfering communication with the target satellite over alarge geographic area. As described in more detail below, the antennasystem includes an adaptive pointing system that controls pointing ofthe target satellite in a manner that takes into consideration theinterference requirements of the other satellites. Using the techniquesdescribed herein, the adaptive pointing system can determine when theamount of interference with one or more non-target satellites, due tothe wide beamwidth axis, reaches a threshold while directly pointed atthe target satellite. In response to the determination, the adaptivepointing system can cause the beam to be pointed in an offset directionaway from the non-target satellite. The offset direction is such thatthe interference requirements with the non-target satellite remainsatisfied, while still permitting communication with the targetsatellite. In doing so, the antenna system described herein can providecommunication with the target satellite at locations where directlypointing at the target satellite is precluded due to interferencerequirements. As a result, the area over which services provided by thetarget satellite can be delivered to users of the antenna system can belarger than compared to the antenna system only directly pointing at thetarget satellite.

FIG. 1 illustrates an example satellite communications system 100 inwhich an antenna system 150 as described herein can be used to pointtowards satellite 110 (referred to hereinafter as “target satellite110”), while also avoiding excessive interference with one or more othersatellites. Many other configurations are possible having more or fewercomponents than the satellite communications system 100 of FIG. 1.

In the illustrated embodiment, the antenna system 150 is mounted onaircraft 102, which in this example is an airplane. More generally, theantenna system 150 can be mounted on various types of mobile vehiclessuch as aircraft (e.g., airplanes, helicopters, drones, blimps,balloons, etc.), trains, automobiles (e.g., cars, trucks, busses, etc.),watercraft (e.g., private boats, commercial shipping vessels, cruiseships, etc.) and others. In the following examples, the techniquesdescribed herein for performing adaptive pointing operations aredescribed in conjunction with the aircraft 102. Alternatively, theadaptive pointing operations may be used in conjunction with othermobile vehicles such as those mentioned above. In yet other embodiments,the adaptive pointing operations may be used in conjunction with anomadic or portable antenna system, such as being associated with abuilding or structures that are not regularly mobile.

As described in more detail below, the antenna system 150 includes anantenna 152 producing a beam that facilitates communication between theaircraft 102 and the target satellite 110. The beam of the antenna 152has an asymmetric beam pattern at some or all of the pointing directionstowards the target satellite 110. The antenna 152 can be any type ofantenna that produces an asymmetric beam pattern, and can vary fromembodiment to embodiment.

In some embodiments, the antenna 152 has a non-circular aperture thatresults in an asymmetric beam pattern at boresight. For example, in theillustrated example of FIG. 1, the antenna 152 is a direct radiatingtwo-dimensional array. In such a case, the beam of the antenna 152 canhave an asymmetric beam pattern that does not vary with pointingdirection. In other embodiments, the beam has an asymmetric beam patternat less than all of the pointing directions towards the targetsatellite. For example, the antenna 152 may be a circularly-shapedtwo-dimensional array that is a non-movable, fully electronic scannedphased array antenna. In such a case, the beam pattern may besymmetrical at boresight, and become asymmetric when the beam is scannedaway from boresight.

The asymmetric beam pattern of the beam of the antenna has a narrowbeamwidth axis and a wide beamwidth axis. As described in more detailbelow, when the antenna system 150 is at certain geographic locations,the wide beamwidth axis can give rise to excessive interference with thenon-target satellite 120, if the beam of the antenna 152 were pointeddirectly at the target satellite 110.

The antenna system 150 also includes a pointing adjustment mechanismsuch as a mechanical positioner (not shown) responsive to a controlsignal from an antenna control unit (not shown) to provide pointing ofthe beam of the antenna 152 towards the target satellite 110 using thetechniques described herein. In some embodiments described herein theantenna system 150 is used for bidirectional (two-way) communicationwith the target satellite 110. In other embodiments, the antenna system150 may be used for unidirectional communication with the targetsatellite 110, such as a receive-only implementation (e.g., receivingsatellite broadcast television). Although only one antenna system 150 isillustrated in FIG. 1 to avoid over complication of the drawing, thesatellite communications system 100 may include many antenna systems150.

As used herein, a beam of an antenna that is pointed “directly” at atarget satellite is pointed such that pointing error (if any) betweenthe boresight direction of maximum gain of the beam and the direction ofthe target satellite is unintentional or undesired. When pointeddirectly, the direction of the target satellite may be the boresightdirection of maximum gain of the beam. Alternatively, when directlypointed, the gain of the beam in the direction of the target satellitemay be less than the maximum gain of the beam. This may for example bedue to pointing accuracy limitations of the antenna.

In the illustrated embodiment, the target satellite 110 providesbidirectional communication between the aircraft 102 and a gatewayterminal 130. The gateway terminal 130 is sometimes referred to as a hubor ground station. The gateway terminal 130 includes an antenna totransmit a forward uplink signal 140 to the target satellite 110 andreceive a return downlink signal 142 from the target satellite 110. Thegateway terminal 130 can also schedule traffic to the antenna system150. Alternatively, the scheduling can be performed in other parts ofthe satellite communications system 100 (e.g., a core node, or othercomponents, not shown). Signals 140, 142 communicated between thegateway terminal 130 and the target satellite 110 can use the same,overlapping, or different frequencies as signals 114, 116 communicatedbetween the target satellite 110 and the antenna system 150.

Network 135 is interfaced with the gateway terminal 130. The network 135can be any type of network and can include for example, the Internet, anIP network, an intranet, a wide area network (WAN), a virtual LAN(VLAN), a fiber optic network, a cable network, a public switchedtelephone network (PSTN), a public switched data network (PSDN), apublic land mobile network, and/or any other type of network supportingcommunication between devices as described herein. The network 135 caninclude both wired and wireless connections as well as optical links.The network 135 can connect multiple gateway terminals 130 that can bein communication with target satellite 110 and/or with other satellites.

The gateway terminal 130 can be provided as an interface between thenetwork 135 and the target satellite 110. The gateway terminal 130 canbe configured to receive data and information directed to the antennasystem 150 from a source accessible via the network 135. The gatewayterminal 130 can format the data and information and transmit forwarduplink signal 140 to the target satellite 110 for delivery to theantenna system 150. Similarly, the gateway terminal 130 can beconfigured to receive return downlink signal 142 from the targetsatellite 110 (e.g., containing data and information originating fromthe antenna system 150) that is directed to a destination accessible viathe network 135. The gateway terminal 130 can also format the receivedreturn downlink signal 142 for transmission on the network 135.

The target satellite 110 can receive the forward uplink signal 140 fromthe gateway terminal 130 and transmit corresponding forward downlinksignal 114 to the antenna system 150. Similarly, the target satellite110 can receive return uplink signal 116 from the antenna system 150 andtransmit corresponding return downlink signal 142 to the gatewayterminal 130. The target satellite 110 can operate in a multiple spotbeam mode, transmitting and receiving a number of narrow beams directedto different regions on Earth. Alternatively, the target satellite 110can operate in wide area coverage beam mode, transmitting one or morewide area coverage beams.

The target satellite 110 can be configured as a “bent pipe” satellitethat performs frequency and polarization conversion of the receivedsignals before retransmission of the signals to their destination. Asanother example, the target satellite 110 can be configured as aregenerative satellite that demodulates and remodulates the receivedsignals before retransmission.

As shown in FIG. 1, the satellite communications system 100 alsoincludes another satellite 120 (hereinafter referred to as “non-targetsatellite 120”). Communication of one or more signals between thenon-target satellite 120 and the antenna system 150 is undesired orunintended. Although only one non-target satellite 120 is illustrated inFIG. 1 to avoid over complication of the drawing, the satellitecommunications system 100 can include many more non-target satellites120 and the techniques described herein can be used to avoid excessiveinterference with each of the non-target satellites 120.

The non-target satellite 120 can, for example, be configured as a bentpipe or regenerative satellite. The non-target satellite 120 cancommunicate one or more signals with one or more ground stations (notshown) and/or other terminals (not shown).

As mentioned above, the antenna system 150 includes antenna 152 thatproduces a beam pointed towards the target satellite 110 via thepointing adjustment mechanism to provide for transmission of the returnuplink signal 116 and reception of the forward downlink signal 114.

Based on the location of the target satellite 110, the location andattitude (yaw, roll and pitch) of the aircraft 102, and the pointingoperational mode controlled by the adaptive pointing system (discussedin more detail below), the antenna control unit of the antenna system150 provides a control signal to the pointing adjustment mechanism tochange the pointing direction of the beam of the antenna 152 to trackthe target satellite 110 as the aircraft 102 moves.

As described in more detail below, the antenna system 150 also includesan adaptive pointing system (not shown) that controls the pointing ofthe beam of the antenna 152 towards the target satellite 110 in a mannerthat takes into consideration the interference requirement of thenon-target satellite 120. As a result, the techniques described hereincan ensure that the interference generated is within acceptable limits,while at the same time permitting communication between the aircraft 102and the target satellite 110. The adaptive pointing system and theadaptive pointing operations are described in more detail below withrespect to FIG. 2 and others.

As used herein, interference “with” the non-target satellite 120 canrefer to uplink interference and/or downlink interference. Uplinkinterference is interference to the non-target satellite 120 caused by aportion of the return uplink signal 116 transmitted by the antennasystem 150 that is received by the non-target satellite 120. Downlinkinterference is interference to the antenna system 150 caused by aportion of a signal transmitted by the non-target satellite 120 that isreceived by the antenna system 150.

In the illustrated embodiment, the target satellite 110 and thenon-target satellite 120 are each geostationary satellites. Thegeostationary orbit slots, and thus the angular separation along thegeostationary arc between the target satellite 110 and the non-targetsatellite 120, can vary from embodiment to embodiment. In someembodiments, the angular separation along the geostationary arc is atleast two degrees. In alternative embodiments, one or both of the targetsatellite 110 and the non-target satellite 120 can be anon-geostationary satellite, such as a LEO or MEO satellite.

FIG. 2 is a block diagram illustrating an example antenna system 150 onthe aircraft 102 of FIG. 1. Many other configurations are possiblehaving more or fewer components than the antenna system 150 shown inFIG. 2. Moreover, the functionalities described herein can bedistributed among the components in a different manner than describedherein.

The antenna system 150 includes antenna 152 that is housed under radome200 disposed on the top of the fuselage or other location (e.g., on thetail, etc.) of the aircraft 102. The antenna 152 produces a beam thatcan provide for transmission of the return uplink signal 116 andreception of the forward downlink signal 114 to support two-way datacommunication between data devices 260 within the aircraft 102 and thenetwork 135 via target satellite 110 and gateway terminal 130. The datadevices 260 can include mobile devices (e.g., smartphones, laptops,tablets, netbooks, and the like) such as personal electronic devices(PEDs) brought onto the aircraft 102 by passengers. As further examples,the data devices 260 can include passenger seat back systems or otherdevices on the aircraft 102. The data devices 260 can communicate withnetwork access unit 340 via a communication link that can be wired orwireless. The communication link can be, for example, part of a localarea network such as a wireless local area network (WLAN) supported bywireless access point (WAP) 250. One or more WAPs can be distributedabout the aircraft 102, and can, in conjunction with network access unit240, provide traffic switching or routing functionality. The networkaccess unit 240 can also allow passengers to access one or more servers(not shown) local to the aircraft 102, such as a server that providesin-flight entertainment.

In operation, the network access unit 240 can provide uplink datareceived from the data devices 260 to modem 230 to generate modulateduplink data (e.g., a transmit IF signal) for delivery to transceiver210. The transceiver 210 can then upconvert and then amplify themodulated uplink data to generate the return uplink signal 116 fortransmission to the target satellite 110 via the antenna 152. Similarly,the transceiver 210 can receive the forward downlink signal 114 from thetarget satellite 110 via the antenna 152. The transceiver 210 canamplify and then downconvert the forward downlink signal 114 to generatemodulated downlink data (e.g., a receive IF signal) for demodulation bythe modem 230. The demodulated downlink data from the modem 230 can thenbe provided to the network access unit 240 for routing to the datadevices 260. The modem 230 can be integrated with the network accessunit 240, or can be a separate component, in some examples.

In the illustrated embodiment, the transceiver 210 is located outsidethe fuselage of the aircraft 102 and under the radome 200.Alternatively, the transceiver 210 can be located in a differentlocation, such as within the aircraft interior.

In the illustrated embodiment and subsequent examples, the antennasystem 150 includes positioner 220 coupled to the antenna 152.Alternatively, the antenna system 150 may include a different pointingadjustment mechanism that may vary from embodiment to embodiment, andmay depend on the antenna type of the antenna 152.

The positioner 220 is responsive to a control signal on line 272 fromantenna control unit 270 to mechanically point the beam of the antenna152 in the direction of the target satellite 110 as the aircraft 102moves. Accordingly, the values of the control signal on line 272 toadjust the angular position of the beam depend on the manner in whichthe positioner 220 (or other pointing adjustment mechanism) iscontrolled, and can vary from embodiment to embodiment. Although only asingle line 272 and a single control signal are shown in FIG. 2, as usedherein “control signal” can include one or more separate control signalsprovided by the antenna control unit 270 to the positioner 220 (or otherpointing adjustment mechanism), which in turn may be provided on one ormore lines. For example, in some embodiments in which the pointingadjustment mechanism adjusts the angular position of the beam inmultiple axes (e.g., azimuth and elevation), the control signal includesa control signal indicating the angular value of each axis.

In some embodiments, the boresight direction of the beam of the antenna152 is fixed relative to the aperture of the antenna 152. For example,the antenna 152 may be a direct radiating two-dimensional array whichresults in boresight being normal to a plane containing the antennaelements of the array. As another example, the antenna 152 may be areflector antenna. In such a case, the antenna 152 can be fullymechanically steered by the positioner 220 to point the beam at thetarget satellite 110. For example, the positioner 220 may be anelevation-over-azimuth (EL/AZ), two-axis positioner that providesadjustment in azimuth and elevation. As another example, the positioner220 may be a three-axis positioner to provide adjustment in azimuth,elevation and skew.

In some embodiments, the antenna 152 is an electro-mechanically steeredarray that includes one mechanical scan axis and one electrical scanaxis. In such a case, the pointing adjustment mechanism can include acombination of mechanical and electrical scanning mechanisms.

In some embodiments, the antenna 152 is a non-movable, fully electronicscanned phased array antenna. In such a case, the pointing adjustmentmechanism can include feed networks and phase controlling devices toproperly phase signals communicated with some or all of the antennaelements of the antenna 152 to scan the beam in azimuth and elevation.

As mentioned above, the antenna control unit 270 provides a controlsignal on line 272 to positioner 220 to point the beam of the antenna152. The functions of the antenna control unit 270 can be implemented inhardware, instructions embodied in memory and formatted to be executedby one or more general or application specific processors, firmware, orany combination thereof.

As shown in FIG. 2, the antenna system 150 also includes adaptivepointing system 274 that controls the pointing operations of the beam ofthe antenna 152 at the target satellite 110 in a manner that takes intoconsideration the interference requirement of the non-target satellite120. In particular, the adaptive pointing system 274 controlstransitioning between a direct pointing operational mode and an offsetpointing operational mode. The direct pointing operational mode(referred to hereinafter as a “first operational mode”) can be used atgeographic locations of the antenna system 150 (and thus aircraft 102)where pointing directly at the target satellite 110 does not give riseto excessive interference with the non-target satellite 120. When theantenna system 150 (and thus the aircraft 102) is at certain geographiclocations, directly pointing the beam at the target satellite 110 issuch that the antenna system 150 still satisfies interferencerequirement with the non-target satellite 120. In other words, at thesecertain geographic locations, the interference due to the wide bandwidthaxis of the beam is within acceptable limits (i.e., below a threshold)of the non-target satellite 120. These certain geographic locations arereferred to herein as an “acceptable geographic area” for using thefirst operational mode. The geographic locations that are within theacceptable geographic area, and whether it is continuous ordiscontinuous, can vary from embodiment to embodiment depending onvarious factors described below. Outside of the acceptable geographicarea, the use of the first operational mode is precluded due to theinterference requirement.

As the aircraft 102 moves around, the adaptive pointing system 274 canswitch to the offset pointing operational mode (referred to hereinafteras a “second operational mode”) when the amount of interference with thenon-target satellite 120, due to the wide beamwidth axis of the beam,reaches a threshold. In the offset pointing operational mode, the beamis pointed in an offset direction away from the non-target satellite120, such that the interference requirement is satisfied while stillpermitting communication with the target satellite 110. As a result, thetechniques described herein can ensure that the interference generatedis within acceptable limits, while at the same time permittingcommunication between the aircraft 102 and the target satellite 110. Inaddition to operating in the offset pointing operational mode, theadaptive pointing system 274 can also change the transmission parametersof the return uplink signal 116 to avoid excessive interference whenneeded. For example, the adaptive pointing system 274 can send commandsto the transceiver 210 to change the transmitted power level of thereturn uplink signal, send commands to the modem 230 to spread thereturn uplink signal over a larger bandwidth, or any other technique forreducing the power spectral density in the direction of the non-targetsatellite 120.

The functions of the adaptive pointing system 274 can be implemented inhardware, instructions embodied in a memory and formatted to be executedby one or more general or application-specific processors, firmware, orany combination thereof. In the illustrated embodiment, the adaptivepointing system 274 is shown as a separate device. Alternatively, someor all of the components or features of the adaptive pointing system 274can be implemented without one or more other components of the antennasystem 150. In the illustrated embodiment, the adaptive pointing system274 is located under the radome 200. Alternatively, some or all of theadaptive pointing system 274 can be located in a different location,such as within the aircraft interior. As another example, some or all ofthe adaptive pointing system 274 may be located in other parts of thesatellite communications system 100, such as the gateway terminal 130, acore node, a network operations center, or other components not shown.

The adaptive pointing system 274 can control transitioning between thefirst operational mode and the second operational mode based on one ormore thresholds for the amount of interference with the non-targetsatellite 120. The one or more thresholds can be based on uplinkinterference and/or downlink interference and can vary from embodimentto embodiment.

In some embodiments, the same threshold can be used for transitioningfrom the first operational mode to the second operational mode, and fortransitioning from the second operational mode to the first operationalmode. In other words, the adaptive pointing system 274 can controltransition from the first operational mode to the second operationalmode when the amount of interference reaches the threshold, and thencontrol transition back to the first operational mode when the amount ofinterference using the first operational mode will be below thethreshold. In some other embodiments, the threshold for transitioningfrom the first operational mode to the second operational mode can bedifferent than the threshold for switching from the second operationalmode to the first operational mode. In such a case, the adaptivepointing system 274 can avoid rapidly switching between the twooperational modes when the aircraft 102 is near the boundary of theacceptable geographic area for using the first operational mode.

In some embodiments, the value(s) of the threshold(s) for transitioningbetween the first and second operational modes can for example be basedon regulatory requirements imposed by regulatory agencies (e.g., FCC,ITU, etc.) on the maximum power spectral density (or other metric) thatcan be radiated to the non-target satellite 120, or coordinationagreements with the operator of the non-target satellite 120.Additionally, the threshold(s) can take into account motion inducedpointing accuracy limitations of the antenna 152, etc.

The adaptive pointing system 274 can determine when to transition basedon a comparison(s) of the threshold(s) to the amount of interferencewith the non-target satellite 120 at the current geographic location andattitude of the aircraft 102. The geographic location of the aircraft102 may for example be obtained via a global positioning system (GPS)271 or other equipment on the aircraft 102. The attitude of the aircraft102 may for example be provided via an inertial reference unit (IRU) 380on the aircraft 102.

The amount of interference at a given geographic location can bedetermined using various techniques, and can be characterized orrepresented in different ways. For example, in some embodiments theamount of interference is represented in terms of power spectral density(PSD).

The amount of uplink interference can for example be determined basedone or more of the known antenna pattern characteristics of the antenna152, the transmission parameters (e.g., transmit power, frequency range,etc.) of the return uplink signal 116, the geographic location of theaircraft 102, the attitude of the aircraft 102, the locations of thetarget satellite 110 and non-target satellite 120, the operatingfrequency, system gain-to-noise temperature (G/T) and/or polarization ofoperation of the non-target satellite 120, etc. Alternatively, otherand/or additional information can be used to calculate the amount ofinterference. The amount of downlink interference can be calculated in asimilar manner based on the parameters of a signal from the non-targetsatellite 120 that is received by the antenna system 150.

In some embodiments, the comparison of the threshold amount ofinterference to the amount of interference at the various geographiclocations if using the first operational mode has been previouslycalculated. In such a case, the adaptive pointing system 274 (or othercomponent) can store a look-up table indicating whether or not using thefirst operational mode is permitted at each the various geographiclocations.

In embodiments in which one or both of the target satellite 110 and thenon-target satellite 120 are non-geostationary satellites, theacceptable geographic area may change over time depending on the currentlocations of the target satellite 110 and the non-target satellite 120.For example, at a first time, the effective angular separation betweenthe target satellite 110 and the non-target satellite 120 as viewed at aparticular geographic location may be small enough that the interferenceusing the first operational mode would exceed the threshold. However, ata second time, due to the movement of the target satellite 110 relativeto the non-target satellite 120, the effective angular separation asviewed at that particular geographic location may be large enough thatthe first operational mode can be used while still satisfying theinterference requirement. In such a case, the look-up table may includethe various possible locations of the target satellite 110 and/or thenon-target satellite 120. The adaptive pointing system 274 may determinewhether or not performing the first mispointing correction operation ispermitted based on the current locations of the target satellite 110and/or the non-target satellite 120.

The manner in which the adaptive pointing system 274 controls thetransition between the first and second operational modes can vary fromembodiment to embodiment. In some embodiments, the adaptive pointingsystem 274 provides an offset vector to the antenna control unit 270indicating the magnitude and direction to adjust pointing of the beamaway from the non-target satellite 120. The offset vector indicates thedirection and amount (e.g., the angular position in the coordinatesystem of the antenna system 150) to change the pointing of the beam ata certain geographic location, relative to a target direction fordirectly pointing at the target satellite 110, in order to satisfy theinterference requirement. The summation of the offset vector and thetarget direction at the target satellite 110, is referred to herein asan offset direction. The offset vector for each of the variousgeographic locations of the aircraft 102 can be pre-computed and storedin the look-up table by the adaptive pointing system 274. The offsetvector may be pre-computed by the adaptive pointing system 274 directly,or pre-computed by one or more other elements of the satellitecommunication system 100 (e.g., the gateway terminal 130, a core node, anetwork operations center or NOC, etc.) and then provided to theadaptive pointing system 274 for storage. The appropriate magnitude anddirection of the offset vector at each geographic location in order tosatisfy the interference requirement can be calculated based on variousfactors such as those discussed above with respect to determining theamount of interference. Alternatively, the manner in which to adjustpointing of the beam away from the non-target satellite 120 may berepresented and performed in other ways.

The location of the offset direction relative to the location of thenon-target satellite 120 can vary from embodiment to embodiment. In someembodiments, the offset direction is directly opposite the non-targetsatellite 120, relative to the target direction for directly pointing atthe target satellite 110. That is, the offset direction and thedirection of the non-target satellite 120 are, when projected onto aplane perpendicular to the target direction, directly opposite (i.e.,rotated 180 degrees) from each other relative to the target direction.In other words, a line within the plane and extending between the offsetdirection of the direction of the non-target satellite 120, intersectsthe target direction. In other embodiments, the offset direction is notdirectly opposite the non-target satellite 120. For example, inembodiments in which there are non-target satellites 120 on both sidesof the target satellite 110, the offset direction may be perpendicularto a line defined by the non-target satellites 120. In some embodiments,non-target satellites 120 may be unevenly distributed on both sides ofthe target satellite 110, such that the absolute value of the respectiveangular separations from the target satellite 110 are not equal. Forexample, one non-target satellite 120 may be offset +2 degrees longitudefrom the target satellite 110 along the geostationary arc, while anothernon-target satellite 120 is offset −4 degrees longitude from the targetsatellite 110 along the geostationary arc. In such a case, the offsetdirection may be towards the non-target satellite 120 having the largerangular separation from the target satellite 110, in order to reduce theamount of interference with the closer non-target satellite 120. Asmentioned above, the transmission parameters of the return uplink signal116 may also be changed to avoid excessive interference when needed.

The adaptive pointing system 274 can then use the current geographiclocation and attitude of the aircraft 102 to retrieve the appropriateoffset vector from the look-up table. In geographic locations within theacceptable geographic area for using the first operational mode, thevalue of the offset vector may be null or zero, such that the antennacontrol unit causes the pointing adjustment mechanism to directly pointthe beam in the target direction at the target satellite 110 when theaircraft 102 is within the acceptable geographic area. In such a case,the transition between the first and second operational modes iscontrolled by the adaptive pointing system 274 based on the offsetvector that is provided to the antenna control unit 270.

Alternatively, other techniques may be used to control transitionbetween the first and second operational modes.

The look-up table may be updated from time to time to reflect changes inone or more non-target satellites 120. The changes may include newnon-target satellites that come into service, changes in the operation(e.g., footprint, operating frequency, operating polarization, changesin orbital position), etc. In embodiments in which the look-up table ispre-computed by the adaptive pointing system 274 directly, dataindicating these changes may be provided to the adaptive pointing system274 such that the look-up table can be updated. In embodiments in whichthe look-up table is pre-computed by another element of the satellitecommunications system 100, that element can update the look-up table andthen provide it to adaptive pointing system 274 for use (e.g., via theforward downlink signal 114).

During operation, as the aircraft 102 moves relative to the targetsatellite 110, the antenna control unit 270 provides the control signalon line 272 to positioner 220 to point the beam of the antenna 152 inthe appropriate direction towards the target satellite 110. The antennacontrol unit 270 may determine the appropriate direction based on thelocation of the target satellite 110, the location of the aircraft 102,the attitude (including yaw, roll, and pitch) of the aircraft 102, andthe offset vector provided by the adaptive pointing system 274. Theantenna control unit 270 may for example store (or otherwise obtain)data indicating the location of the target satellite 110. The geographiclocation of the aircraft 102 may for example be obtained via a globalpositioning system (GPS) 271 or other equipment on the aircraft 102. Theattitude of the aircraft 102 may for example be provided via an inertialreference unit (IRU) 380 on the aircraft 102.

FIG. 3 illustrates a perspective view of an example of antenna 152 andpositioner 220 of antenna system 150. In the illustrated embodiment, theantenna 152 includes an array 310 of antenna elements that is a directradiating two-dimensional array which results in boresight being normalto a plane containing the antenna elements of the array 310.Alternatively, the array 310 of antenna elements can be arranged or fedin a different manner such that boresight is not normal to the planecontaining the antenna elements of the array 310. As mentioned above, inother embodiments the antenna type of the antenna 152 may be different.

In the illustrated embodiment, the array 310 has a non-circular aperturethat includes a major axis 312 (referred to hereinafter as “horizontalaxis 312”), which is the longest line through the center of the array310 of antenna elements. The array 310 of antenna elements also includesa minor axis (referred to hereinafter as “vertical axis 314”), which isthe shortest line through the center of the array 310 of antennaelements. The non-circular aperture of the array 310 of antenna elementsdefines a beam having an asymmetric beam pattern at boresight.

As mentioned above, in the illustrated embodiment the boresightdirection of maximum gain is normal to a plane containing the antennaelements of the array 310. As a result, in the illustrated embodimentthe asymmetric beam pattern has a narrow beamwidth axis aligned with thehorizontal axis 312 and a wide beamwidth axis aligned with the verticalaxis 314. Alternatively, the array 310 of antenna elements can bearranged and/or fed such that boresight is not normal to the planecontaining the antenna elements of the array 310.

The positioner 220 is responsive to control signal provided by theantenna control unit 270 (see FIG. 2) to point the beam of the antenna152 using the techniques described herein. In the illustratedembodiment, the positioner 220 is an elevation-over-azimuth (EL/AZ)two-axis positioner that provides full two-axis mechanical steering. Thepositioner 220 includes a mechanical azimuth adjustment mechanism tomove the beam of the antenna 152 is azimuth 320, and a mechanicalelevation adjustment mechanism to move the beam of the antenna 152 iselevation 340. Each of the mechanical adjustment mechanisms can forexample include a motor with gears and other elements to provide formovement of the antenna 152 around a corresponding axis. As mentionedabove, in other embodiments the pointing adjustment mechanism used topoint the beam of the antenna 152 may be different than positioner 220.

FIG. 4A illustrates a perspective view of the beam 422 of an exampleasymmetric beam pattern of an example antenna 152. The beam 422 has a3-dB (half-power) contour with an elliptical shape about boresight 430.The positioner 300 (FIG. 3) or other pointing adjustment mechanism canmove the antenna 152 to point the boresight 430 of the beam towards thetarget satellite 110. The direction can be described in terms of azimuth424 and elevation 434. Azimuth refers to the angle between boresight 430and reference 402, and elevation 434 refers to the angle betweenboresight 430 and horizon 401.

FIG. 4B illustrates an example half-power contour of the asymmetric beampattern of beam 422 of FIG. 4A. The beam 422 has a first half-powerbeamwidth (hereinafter referred to as “horizontal half-power beamwidth”)along the narrow beamwidth axis 440 that corresponds to the horizontalaxis 312 of the antenna 152, and a second half-power beamwidth(hereinafter referred to as “vertical half-power beamwidth”) along thewide beamwidth axis 450 corresponding to the vertical axis 314 of theantenna 152. The horizontal half-power beamwidth and the verticalhalf-power beamwidth can vary from embodiment to embodiment. In someembodiments, the vertical half-power beamwidth is at least three timesgreater than the horizontal half-power beamwidth, such as being fourtimes greater. For example, in some embodiments the vertical half-powerbeamwidth can be less than three degrees, such as being at least fourtimes greater. For example, in some embodiments the vertical half-powerbeamwidth can be less than three degrees, and the horizontal half-powerbeamwidth can be less than one degree. Alternatively, the verticalhalf-power beamwidth and the horizontal half-power beamwidth may bedifferent than the examples above.

As shown in FIG. 4B, the beam 422 has a skew angle 460. As used herein,“skew angle” refers to the angle between the narrow beamwidth axis ofthe beam of an antenna (e.g., narrow beamwidth axis 440 of the beam422), and a line defined by the target satellite 110 and the non-targetsatellite 120. The half-power beamwidth of the beam 422 along the linedefined by the target satellite 110 and the non-target satellite 120 isreferred to herein as a “composite half-power beamwidth” 470. Thecomposite half-power beamwidth 470 is a mixture of the half-powerbeamwidths along the narrow beamwidth axis 440 and the wide beamwidthaxis 450 respectively, and depends on the skew angle 460. For example,in embodiments in which the target satellite 110 and the non-targetsatellite 120 are geostationary satellites along the geostationary arc,the skew angle 460 is the angle between the narrow beamwidth axis 440and the geostationary arc, and the composite half-power beamwidth 470 isthe beamwidth along the geostationary arc.

The skew angle 460, and thus the composite half-power beamwidth 470,varies depending upon the geographic location of the antenna system 150(and thus aircraft 102). For example, if the antenna system 150 islocated at the same longitude as the target satellite 110, the skewangle 460 is zero degrees and the composite half-power beamwidth 470 isthe horizontal half-power beamwidth along the narrow beamwidth axis 440.In such a case, the composite half-power beamwidth 470 can be narrowenough to satisfy interference requirement with the non-target satellite120 while in the first operational mode of directly pointing the beam422 at the target satellite 110.

However, if the antenna system 150 is located at a different longitudethan the target satellite 110, the skew angle 460 is non-zero and thecomposite half-power beamwidth 470 is a mixture of the verticalhalf-power beamwidth and the horizontal half-power beamwidth. As aresult, at certain geographic locations, the composite half-powerbeamwidth 470 can be wide enough to cause excessive interference withthe non-target satellite 120, if the beam 422 were directly pointed atthe target satellite 110 using the first operational mode. In otherwords, due to the vertical half-power beamwidth along the wide beamwidthaxis 450, at certain geographic locations within the service area of thetarget satellite 110, the interference level could exceed the thresholdamount of interference with the non-target satellite 120 if the beam 422were directly pointed at the target satellite 110. In such a case, asdescribed herein, the adaptive pointing system 274 causes the antennasystem 150 to operate in the second operational mode in which the beam422 is pointed in an offset direction away from the non-target satellite120, such that the interference requirement is satisfied while stillpermitting communication with the target satellite 110.

FIG. 5A illustrates an example acceptable geographic area 510 a, 510 bfor the first operational mode of directly pointing the beam at thetarget satellite 110. FIG. 5A also illustrates an example acceptablegeographic area 510 c, 510 d for the second operational mode of pointingthe beam in an offset direction away from the non-target satellite 120.In the illustrated embodiment, the target satellite 110 and thenon-target satellite 120 are both geostationary satellites.

The acceptable geographic area 510 a, 510 b are geographic locations ofthe antenna system 150 where the amount of interference with thenon-target satellite 120 is at or below the threshold when the beam 422is directly pointed at the target satellite 110. In other words, withinthe acceptable geographic area 510 a, 510 b, the skew angle is less thanthe maximum acceptable skew angle that satisfies the interferencerequirement with the non-target satellite 120. The boundary 510corresponds the maximum acceptable skew angle at which the beam 422 canbe directly pointed at the target satellite 110.

The maximum acceptable skew angle, and thus the acceptable geographicarea 510 a, 510 b of the first operational mode, can vary fromembodiment to embodiment. The maximum acceptable skew angle can dependon the radiation pattern of the antenna 152, the locations of the targetsatellite 110 and non-target satellite 120, the threshold amount ofinterference with the non-target satellite 120, the transmissionparameters of the return uplink signal 116, etc.

FIG. 5A also includes example acceptable geographic area 510 c, 510 dfor using the second operational mode when the aircraft 102 is outsidethe acceptable geographic area 510 a, 510 b of the first operationalmode. The acceptable geographic area 510 c, 510 d are geographiclocations where the amount of interference with the non-target satellite120 when using the second operational mode is at or below the threshold,and signal communication with the target satellite 110 has acceptable ordesired performance characteristics. In the illustrated example, theacceptable geographic area 510 c, 510 d includes all of the geographiclocations outside the acceptable geographic area 510 a, 510 b of thefirst operational mode. In other words, the magnitude of the offsetneeded to satisfy the interference requirement of the non-targetsatellite 120 during the second operational mode, is such thatacceptable signal communication performance can be achieved between theaircraft 102 and the target satellite 110 everywhere outside theacceptable geographic area 510 a, 510 b of the first operational mode.

In other examples, the acceptable geographic area 510 c, 510 d does notinclude all of the geographic locations outside the acceptablegeographic area 510 a, 510 b of the first operational mode. In such acase, the acceptable geographic area 510 c, 510 d includes a boundaryrepresenting the minimum acceptable performance characteristic forsignal communication between the aircraft 102 and the target satellite110 when using the second operational mode. At high scan angle values(e.g., at lower latitudes near the equator 500), the boundary can be dueto the increasing magnitude of the offset needed to satisfy theinterference requirement of the non-target satellite 120. As a result,at certain geographic locations corresponding to a scan angle value ator above a maximum value (e.g., 85 degrees), the magnitude of the offsetneeded may preclude signal communication between the aircraft 102 andthe target satellite 110 having at least the minimum acceptableperformance characteristic.

In some embodiments in which the asymmetric beam pattern of the antenna152 changes with pointing direction, the boundary of the acceptablegeographic area 510 c, 510 d can also be due to an increase in thecomposite half-power beamwidth of the beam 422 with pointing direction.For example, in embodiments in which the antenna 152 is anelectronically scanned phased array, one or more of the beamwidths ofthe beam 422 change with scan angle. At low latitudes near the equator500, the boundary can be due to an increase in the composite half-powerbeamwidth of the beam 422 at larger scan angles to the target satellite110.

The minimum acceptable performance characteristic can be represented invarious ways, and can vary from embodiment to embodiment. For example,the minimum acceptable performance characteristic can be a minimumacceptable data rate for signal communication between the aircraft 102and the target satellite 110 that can be achieved for a certain amountof system resource usage (e.g., capacity, bandwidth, etc). As anotherexample, the minimum acceptable performance characteristic cancorrespond to a maximum acceptable reduction in gain in the direction ofthe target satellite 110. In other words, as the magnitude of the offsetincreases, the gain of the beam in the direction of the target satellite110 decreases. In such a case, the minimum acceptable performancecharacteristic corresponds to a maximum difference between the boresightdirection of maximum gain of the beam and the gain in the direction ofthe target satellite 110.

The union of the acceptable geographic area 510 a, 510 b for using thefirst operational mode and the acceptable geographic area 510 c, 510 dfor using the second operational mode, results in a composite acceptablegeographic area for the aircraft 102 to communicate with the targetsatellite 110. As discussed above, the first operational mode ispreferred because it can be used to provide more efficient communicationwith the target satellite than the second operational mode. However, byoperating in the second operational mode, the aircraft 102 is permittedto continue signal communication with the target satellite 110 ingeographic locations where use of the first operating mode is precludeddue to the interference requirements. As a result, the service area overwhich services provided by the target satellite 110 can be delivered tousers on the aircraft 102 can be larger than compared to only using thefirst operational mode.

FIG. 5B illustrates pointing of the beam 422 of the antenna 152 for anexample geographic location 520 within the acceptable geographic area510 a, 510 b for using the first operational mode. At this location 520,the composite half-power beamwidth along the geo arc 540 is small enoughthat the beam can be directly pointed at target satellite 110. Thedirection of boresight 430 of the beam 422 when using the firstoperational mode is referred to herein as the target direction. In theillustrated example, the target direction is the actual direction of thetarget satellite 110. Alternatively, the target direction may bedifferent than the actual direction of the target satellite 110 due topointing accuracy limitations of the antenna 152.

FIG. 5C illustrates pointing of the beam 422 of the antenna 152 for anexample geographic location 530 outside the acceptable geographic area510 a, 510 b for using the first operational mode. In this example, thegeographic location 530 is within the acceptable geographic area 510 c,510 d for using the second operational mode. As can be seen in FIG. 5C,boresight 430 of the beam 422 is pointed to an offset direction 590 awayfrom the non-target satellite 120, such that the interferencerequirements are satisfied. In the illustrated example, the offsetdirection 590 is in the opposite direction of the non-target satellite120 along the geo arc 540. In other examples, the offset direction 590is not along the geo arc 540. For example, the offset direction 590 maybe perpendicular to the geo arc 540, or any other direction that reducesthe amount of interference with the non-target satellite 120 below thethreshold and permits acceptable signal communication with the targetsatellite 110.

FIG. 5D illustrates a cross-sectional view of a portion of the beampattern of the beam 422 versus angle along the geo arc 540 for thepointing example of FIG. 5C. Line 560 represents the maximum value ofthe gain in the direction of non-target satellite 120 that satisfies theinterference requirement with the non-target satellite 120.

Plot 562 shows what the beam pattern would be if the beam were directlypointed at the target satellite 110 using the first operational mode. Ascan be seen in FIG. 5D, in such a case the amount of interference in thedirection of the non-target satellite 560 would be above the line 560.

Plot 564 shows the beam pattern using the second operational mode ofpointing to the offset direction 590. As can be seen in FIG. 5D, bypointing in the offset direction 590, the amount of interference in thedirection of the non-target satellite 560 satisfies the interferencerequirement with the non-target satellite 120. In addition, due to theoff-axis gain roll-off of the beam pattern, the reduction 566 in thegain in the direction of the non-target satellite 120 is greater thanthe reduction in gain 568 in the direction of the target satellite 110.In other words, by pointing in the offset direction 590, the amount ofinterference in the direction of non-target satellite 120 is decreasedby an amount (e.g., 15 dB) that is more than the gain in the directionof the target satellite 110 decreases (e.g., 1 dB). As a result,pointing in the offset direction 590 can have less of a detrimentaleffect on the link performance with target satellite 110 than othertechniques for reducing interference such as reducing the transmitpower. For example, if the beam were pointed directly pointed at thetarget satellite 110 and the transmit power were reduced by an amountsufficient to satisfy the interference requirement, the power in thedirection of the target satellite 110 would also be reduced by the sameamount. By pointing in the offset direction 590, the power in thedirection of the target satellite 110 is reduced by less than that.

When in the second operational mode, the manner in which the offsetmagnitude and direction changes to adjust pointing of the beam away fromthe non-target satellite 120 as the aircraft 102 moves can vary fromembodiment to embodiment. FIG. 5E is the same as FIG. 5A and includesline 550 representing an example flight path for the aircraft 102between source 552 and destination 554. At geographic locations along afirst segment 570 of the flight path, the aircraft 102 is within theacceptable geographic area 510 b for using the first operational mode.Thus, along the first segment 570 the adaptive pointing system 274operates the antenna system 150 in the first operational mode ofdirectly pointing at the target satellite 110. At geographic location556 the aircraft 102 leaves the acceptable geographic area 510 b of thefirst operational mode and enters the acceptable geographic area 510 dof the second operational mode. Thus, at geographic location 556 theadaptive pointing system 274 controls transition from the firstoperational mode to the second operational mode, and the antenna system150 continues to operate in the second operational mode along thesegment 572.

At geographic location 558 the aircraft 102 enters the acceptablegeographic area 510 a of the first operational mode. Thus, at geographiclocation 558 the adaptive pointing system 274 controls transition fromthe second operational mode to the first operational mode, and theantenna system 150 continues to operate in the first operational modealong the segment 574 to the destination 554. As described above, themanner in which the adaptive pointing system 274 controls transitionbetween the first and second operational modes can vary from embodimentto embodiment. In some embodiments, the transition is controlled by thevalue of the offset vector that is provided by the adaptive pointingsystem 274.

When operating in the second operational mode, the manner in which theadaptive pointing system 274 controls changes in the offset direction asthe aircraft 102 moves along segment 572 can vary from embodiment toembodiment. In some embodiments, the offset direction is changedcontinually by adjusting at least one of the direction and amount of theoffset vector to reflect the changes in the geographic location of theaircraft 102. For example, the adaptive pointing system 274 maycontinuously monitor the current geographic location of the aircraft 102at a certain rate (e.g., 5 Hz) and provide the appropriate offset vectorfor that location. In other embodiments, the offset vector is changed ona periodic basis. For example, the adaptive pointing system 274 mayperiodically obtain the current geographic location of the aircraft 102and provide the appropriate offset vector for that location.

FIG. 6 illustrates an example adaptive pointing operation 600 forpointing the beam of antenna 152 at the target satellite 110. Otherembodiments can combine some of the steps, can perform the steps indifferent orders and/or perform different or additional steps than theones illustrated in FIG. 6.

During step 602, the aircraft 102 is within the acceptable geographicarea of the first operational mode. As a result, the adaptive pointingsystem 274 controls the antenna system 150 to operate in the firstoperational mode to point the beam of the antenna 152 in the targetdirection at the target satellite 110. As described above, the targetdirection of the beam may be different than the actual direction of thetarget satellite 110 due to pointing accuracy limitations.

Also during step 602, a signal is communicated between the antennasystem 150 on the aircraft 102 and the target satellite 110. Inembodiments in which the antenna system 150 is in bidirectionalcommunication with the target satellite 110, multiple signals (e.g.,forward downlink signal 114, and return uplink signal 116) may becommunicated during this step. As the aircraft 102 moves relative to thetarget satellite 110, the antenna control unit 270 provides the controlsignal on line 272 to positioner 220 to point the beam in the targetdirection in order to track the target satellite 110.

At step 604, the determination is made as to whether the amount ofinterference with the non-target satellite 120 reaches a threshold dueto the wide beamwidth axis of the asymmetric beam pattern of the antenna152. This may for example be done by determining whether or not theaircraft 102 is within the acceptable geographic area of the firstoperational mode. If not, the operation 600 returns to step 602 andcontinues to operate in the first operational mode.

If the determination is made at step 604 that the amount of interferencewith the non-target satellite 120 reaches the threshold, the adaptivepointing operation 600 continues to step 606. In step 606, the adaptivepointing system 274 controls transition from the first operational modeto the second operational mode in which the beam is adjusted to anoffset direction away from the non-target satellite 120.

At step 608, the antenna system 150 operates in the second operationalmode and further communicates the signal with the target satellite 110.During step 808, the adaptive pointing system 274 may update the offsetdirection as the aircraft 102 moves.

At step 610, the determination is made as to whether the amount ofinterference with the non-target satellite 120 using the firstoperational mode will be below the threshold. This may for example bedone by determining whether or not the aircraft 102 has entered theacceptable geographic area of the first operational mode. If not, theoperation 600 returns to step 608 and continues using the secondoperational mode.

If the determination is made at step 610 that the amount of interferencewith the non-target satellite 120 using the first operational mode willbe below the threshold, the operation 600 returns to step 602 and theadaptive pointing system 274 controls transition back to the firstoperational mode.

In examples described above, the adaptive pointing operations describedherein are described in conjunction satisfying the interferencerequirements of the non-target satellite 120. More generally, theadaptive pointing operations described herein can be used in conjunctionwith satisfying interference requirements with non-satellite objects,such as celestial sources, terrestrial sources, airborne sources such asaircraft, drones, blimps, etc. Additionally, the adaptive pointingoperations described herein may generally be used to satisfyinterference requirements in a non-target direction, regardless ofwhether there is an actual object in the non-target direction.

The methods disclosed herein include one or more actions for achievingthe described method. The methods and/or actions can be interchangedwith one another without departing from the scope of the claims. Inother words, unless a specific order of actions is specified, the orderand/or use of specific actions can be modified without departing fromthe scope of the claims.

The functions described can be implemented in hardware, software,firmware, or any combination thereof If implemented in software, thefunctions can be stored as one or more instructions on a tangiblecomputer-readable medium. A storage medium can be any available tangiblemedium that can be accessed by a computer. By way of example, and notlimitation, such computer-readable media can include RAM, ROM, EEPROM,CD-ROM, or other optical disk storage, magnetic disk storage, or othermagnetic storage devices, or any other tangible medium that can be usedto carry or store desired program code in the form of instructions ordata structures and that can be accessed by a computer. Disk and disc,as used herein, include compact disc (CD), laser disc, optical disc,digital versatile disc (DVD), floppy disk, and Blu-ray® disc where disksusually reproduce data magnetically, while discs reproduce dataoptically with lasers.

A computer program product can perform certain operations presentedherein. For example, such a computer program product can be a computerreadable tangible medium having instructions tangibly stored (and/orencoded) thereon, the instructions being executable by one or moreprocessors to perform the operations described herein. The computerprogram product can include packaging material. Software or instructionscan also be transmitted over a transmission medium. For example,software can be transmitted from a website, server, or other remotesource using a transmission medium such as a coaxial cable, fiber opticcable, twisted pair, digital subscriber line (DSL), or wirelesstechnology such as infrared, radio, or microwave.

Further, modules and/or other appropriate means for performing themethods and techniques described herein can be downloaded and/orotherwise obtained by suitable terminals and/or coupled to servers, orthe like, to facilitate the transfer of means for performing the methodsdescribed herein. Alternatively, various methods described herein can beprovided via storage means (e.g., RAM, ROM, a physical storage mediumsuch as a CD or floppy disk, etc.), such that a user terminal and/orbase station can obtain the various methods upon coupling or providingthe storage means to the device. Moreover, any other suitable techniquefor providing the methods and techniques described herein to a devicecan be utilized. Features implementing functions can also be physicallylocated at various positions, including being distributed such thatportions of functions are implemented at different physical locations.

While the present disclosure is disclosed by reference to the preferredembodiments and examples detailed above, it is to be understood thatthese examples are intended in an illustrative rather than in a limitingsense. It is contemplated that modifications and combinations willreadily occur to those skilled in the art, which modifications andcombinations will be within the spirit of the invention and the scope ofthe following claims.

What is claimed is:
 1. A method comprising: identifying a targetsatellite associated with a target direction and a non-target satelliteassociated with a non-target direction; identifying a characteristicassociated with communication of signals by the non-target satellite;determining, based at least in part on the characteristic, that anamount of interference to the non-target satellite of a beam pointed inthe target direction exceeds a threshold; pointing, in response to thedetermination that the amount of interference of the beam to thenon-target satellite exceeds the threshold, the beam to an offsetdirection away from the target direction; and communicating a signalwith the target satellite over the beam with the beam pointed in theoffset direction.
 2. The method of claim 1, wherein the characteristiccomprises an operating frequency, a system gain-to-noise temperature ofthe non-target satellite, a polarization, or a combination thereof. 3.The method of claim 2, wherein determining that the amount ofinterference to the non-target satellite of the beam pointed in thetarget direction comprises: determining that the operating frequencyassociated with communicating signals with the non-target satellitecorresponds to a second operating frequency associated withcommunicating signals with the target satellite, determining that thepolarization associated with the signals communicated with thenon-target satellite corresponds to a second polarization associatedwith communicating signals with the target satellite, or a combinationthereof.
 4. The method of claim 1, further comprising: determining thata geographic location of the mobile vehicle is outside of a regionassociated with an acceptable amount of interference in the non-targetdirection, wherein identifying the characteristic associated withcommunication of signals by the non-target satellite comprisesidentifying the characteristic based at least in part on thedetermination that the geographic location of the mobile vehicle isoutside of the region.
 5. The method of claim 4, further comprising:changing the offset direction due to a change of the geographic locationof the mobile vehicle to a second geographic location that is alsooutside of the region associated with the acceptable amount ofinterference in the non-target direction.
 6. The method of claim 4,wherein a boundary of the region associated with the acceptable amountof interference in the non-target direction is determined based at leastin part on a skew angle between an asymmetric beam pattern of the beamand a geostationary arc reaching a predetermined value.
 7. The method ofclaim 1, wherein the offset direction is such that a second amount ofinterference of the beam in the non-target direction remains at or belowthe threshold.
 8. The method of claim 1, wherein the mobile vehicle isan aircraft.
 9. An antenna system for mounting on a mobile vehicle, theantenna system comprising: an antenna having a beam for communicating asignal with a target satellite associated with a target direction; apointing adjustment mechanism configured to adjust pointing of the beamof the antenna; and an adaptive pointing system configured to: identifya non-target satellite associated with a non-target direction; identifya characteristic associated with communication of signals by thenon-target satellite; determine, based at least in part on thecharacteristic, that an amount of interference to the non-targetsatellite of the beam when pointed in the target direction exceeds athreshold; point, in response to the determination that the amount ofinterference of the beam to the non-target satellite exceeds thethreshold, the beam to an offset direction away from the targetdirection; and communicate a signal with the target satellite over thebeam with the beam pointed in the offset direction.
 10. The antennasystem of claim 9, wherein the characteristic comprises an operatingfrequency, a system gain-to-noise temperature of the non-targetsatellite, a polarization, or a combination thereof.
 11. The antennasystem of claim 10, wherein the adaptive pointing system is configuredto determine the amount of interference to the non-target satellite ofthe beam pointed in the target direction by: determining that theoperating frequency associated with communicating signals with thenon-target satellite corresponds to a second operating frequencyassociated with communicating signals with the target satellite,determining that the polarization associated with the signalscommunicated with the non-target satellite corresponds to a secondpolarization associated with communicating signals with the targetsatellite, or a combination thereof.
 12. The antenna system of claim 9,wherein the adaptive pointing system is further configured to: determinethat a geographic location of the mobile vehicle is outside of a regionassociated with an acceptable amount of interference in the non-targetdirection, wherein the adaptive pointing system is configured toidentify the characteristic associated with communication of signals bythe non-target satellite by identifying the characteristic based atleast in part on the determination that the geographic location of themobile vehicle is outside of the region.
 13. The antenna system of claim12, wherein the adaptive pointing system is further configured to:change the offset direction due to a change of the geographic locationof the mobile vehicle to a second geographic location that is alsooutside of the region associated with the acceptable amount ofinterference in the non-target direction.
 14. The antenna system ofclaim 12, wherein a boundary of the region associated with theacceptable amount of interference in the non-target direction isdetermined based at least in part on a skew angle between an asymmetricbeam pattern of the beam and a geostationary arc reaching apredetermined value.
 15. The antenna system of claim 9, wherein theoffset direction is such that a second amount of interference of thebeam in the non-target direction remains at or below the threshold. 16.The antenna system of claim 9, wherein the mobile vehicle is anaircraft.